Stop monkey patching bn.js

[paddyquinn]

Noticed this in dashcore-lib, which is a fork of this lib. The bn.js file within this lib pulls in the bn.js npm module and then dynamically overrides its methods. This makes for a very frustrating developer experience. More details can be found in the issue I opened in dashcore-lib.

[micahriggan]

Agreed, there's a few things in bitcore-lib where we're polluting other modules. An MR to fix that would be greatly appreciated.

[HoOngEe]

Agreed, I also went through an absurd experience. After importing this lib I tried new BN("00cd667f8287be106305f9fa3e2a1706579a179b084dc8247c0e31ebc900df9d", 16).toBuffer("be", 32).length, but it returns 31!
Because this library modifies the method parametrization, I have to use new BN("00cd667f8287be106305f9fa3e2a1706579a179b084dc8247c0e31ebc900df9d", 16).toBuffer({endian: "big", size: 32}).length instead to get intended result.